(a) The Field of the Invention
The present invention relates to an improvement in processes and devices for the continuous spinning of viscose rayon.
(b) The Prior Art
Processes of this kind are known wherein the viscous spinning dope is extruded through suitable spinnerets and coagulated to form filaments which are grouped into multifilament yarns, and stretched, in suitable coagulating and drawing baths, comprising or not comprising guide tubes wherein the yarn travels in equicurrent with respect to the bath, and from which the yarn proceeds to travel in a substantially helicoidal path, that is a path constituted by a series of coils which generally are not helical but are close to helical form. Practically this is effected by passing the yarn over a main or treatment roller having a relatively large diameter, on which the chemical and thermal treatments of the yarn take place, and on an advancement roller having a much smaller diameter than the first one and being askew with respect thereto. Spinning machines of this kind are described and illustrated e.g. in Italian Pat. No. 638,929. It is possible to process a plurality of yarns concurrently, and this is normally done, by passing a plurality of yarns originating from as many spinnerets, over a single treatment roller and over a plurality of advancing rollers, each of these latter corresponding to one yarn. In describing this invention only one advancing roller and therefore the treatment of one yarn will be illustrated, but it should be kept in mind that there will be in practice a plurality of yarns and a corresponding plurality of advancing rollers. The yarn undergoes in its helicoidal travel a succession of treatments generally comprising setting, desulphuration, bleaching, finishing, and the corresponding washings, and may undergo particular coagulating and setting treatments which are not a part of the invention.
In all cases the yarn must be dried at the end of the aforesaid treatments. This is effected by passing the yarn over a zone of the treatment roller which is conveniently heated.